It must have been a weird artifact of my OS upgrade from 10.9 to 10.10.5 on my 2010 15-inch MacBook Pro (which has an SSD I installed to keep it from being slow). After shutting it down for the night and booting it back up, Flux + Chrome work just fine...

For several months now, I've had this problem. Sometimes f.lux continues to work just fine when I have Chrome open, but just as often (if not more so), f.lux fails to work as soon as Chrome is launched. f.lux is still working to SOME degree (I can tell that there's a very slight orange tint on the screen), but as soon as I quit Chrome entirely, it becomes quite clear how much it was not doing what it was supposed to as the screen immediately jumps to a much darker shade. I have 10.10.4 as my OS, but as I've said, this has lasted a while. Only Chrome causes this.

As my recent post shows, I"m having the same problems as I had with Chrome, but with other pieces of software.

I took your advice and installed gfxCardStatus and discovered that Ableton Live, one of the offending apps, switches from "Intel HD Graphics" to "NVIDIA GeForce etc...". Do apps that switch to the NVIDIA card necessarily mean that Flux won't be able to perform?